For the first two videos, maybe the issue is that robot is placed on the middle of the black line.
Maybe to try and place it on the beginning of the line (I guess that is what you tried to do on your 3rd video?).
Also, according instructions, when you press top button robot will begin with spinning if he cannot find the line. Solution is to nudge him closer to the line and then robot will say “Ah-ha” when he finds it.
Believe me I tried many times. I put Botley on top of the line, close to the beginning of the line etc… I also tried lines with different widths and it never worked.
I think the sensor is malfunctioning.
Probably will need to contact robotshop and ask for replacement.
Do you know how I can do this ? Should I call the shop ?